Effect of Mo Dispersion on the Catalytic Properties and Stability of Mo-Fe Catalysts for the Partial Oxidation of Methanol

Mo-Fe catalysts with different Mo dispersions were synthesized with fast (Cat-FS, 600 r center dot min(-1)) or slow stirring speed (Cat-SS, 30 r center dot min(-1)) by the coprecipitation method. Improving the stirring speed strengthened the mixing of the solution and increased the dispersion of particles in the catalyst, which exhibited favorable activity and selectivity. The byproduct (dimethyl ether (DME)) selectivity increased from 2.3% to 2.8% with Cat-SS, while it remained unchanged with Cat-FS in a stability test. The aggregation of particles and thin Mo-enriched surface layer decreased the catalyst surface area and slowed down the reoxidation of reduced active sites with Cat-SS, leaving more oxygen vacancies which promoted the formation of DME by the nonoxidative channel.